A construction project such as a bridge is usually detailed at its edges by a cornice that is principally decorative, although it might also function to enclose and protect piping, a drainage gutter, or the like. The cornice is typically mounted at the upper edge of a vertical surface which in this type of construction is normally itself formed of reinforced concrete.
Casting the cornice in situ is an extremely difficult job, and mounting precast concrete cornice sections on the project is also extremely expensive and time-consuming. Both solutions require that the structure itself be made sufficiently strong to carry the considerable weight of the cornice thereby adding to costs.
Hence it is known to make the cornice up of discrete sections of shaped panels, as in curtain-wall construction. This type of cornice is, nonetheless, still quite difficult to hang correctly. When the structure on which it is to be mounted is slightly out of plumb or does not otherwise conform exactly to the desired shape, as is common in large-scale projects where close tolerances are not critical, it becomes very difficult to mount the cornice in place, keeping it straight and plumb. Furthermore the fairly delicate cornice is often damaged in later phases of construction when installed at the original pour, so that patching or replacing sections of it become necessary